Cancer isn’t the leading cause of death in the United States; heart disease ranks first in that regard. But it’s cancer that strikes fear into the hearts of many Americans.

Cancer can take an excruciating toll on its millions of victims and their family members. Cancer treatments are often highly toxic, and the disease is increasingly striking people at younger ages, which is why it accounts for more years of potential life lost than heart disease.

So when a blood test comes along that claims to be able to screen for over 50 cancers at once in a single blood draw before symptoms appear – as is the case for the Galleri test, by the biotech company GRAIL – it might seem like society has a Holy Grail of modern medicine at their fingertips.

But a closer look at the evidence suggests that the Galleri test is not yet the universal screening breakthrough patients and doctors hope for.

As a physician who studies early cancer detection, and as chair of the American Cancer Society’s screening guideline development group, I have been following this test’s development with interest.

While the Galleri test certainly shows great promise, clinical trial data indicates that it struggles with early-stage cancer detection and has not yet been shown to lower the risk of death from cancer or prevent advanced cancer. Across all cancer stages, the test missed over two-thirds of cancer cases.

On Sept. 23, 2026, an advisory panel to the U.S. Food and Drug Administration voted to recommend approval of the Galleri test. While a recommendation from the FDA’s advisory panel is not the same as full approval from the agency, it marks a critical first step in the process of potentially making the test widely available to the American public. The FDA has not yet announced when it will make a decision on the test.

But even as the advisory panel approved the test, panelists recommended that the word “early” be removed from “early cancer detection test” in product labeling. Panel members were not convinced the test can find cancers at their earliest and most curable stages, and they expressed uncertainty about the test’s benefit to patients at this time.

Given this uncertainty, careful scrutiny of the data behind the test can help doctors and patients make informed decisions about whether to use it.

What is the Galleri test? How does it work?

Galleri is part of an emerging class of multicancer early detection tests. These tests do not diagnose cancer: If a test is positive, further evaluation is necessary to determine whether cancer is present, and, if so, what type of cancer. It is offered as a screening test, similar to mammography for breast cancer screening or PSA testing for prostate cancer screening, but with the potential advantage of screening for many cancers at once, including many for which no screening test currently exists.

The Galleri test looks for DNA fragments in blood that are associated with cancer. When something goes wrong with your DNA, whether because you inherited a mutation or something in your environment triggered that mutation, the processes that regulate cell division can go awry. Uncontrolled cell division can trigger the growth of cancer cells.

Galleri and other multicancer early detection tests in development look for differences that distinguish the DNA produced by tumor cells from normal cells. Galleri identifies unique tags on cancer DNA called methylation markers and uses machine learning algorithms to generate a positive or negative test result.

What are the strengths of the Galleri test?

The Galleri test looks for DNA signals from over 50 cancers, including the 12 that account for almost two-thirds of cancer deaths in the U.S, such as lung and pancreas cancer. Importantly, it provides information on which organ the possible tumor likely originated from. Currently recommended cancer screenings are largely limited to four types of cancer.

Many of the cancers the Galleri test looks for are not currently included in routine screening. Moreover, the test has a very low false positive rate: Only about 0.5% of people who get the test are incorrectly identified as having cancer, or one person out of every 200 tests. A false positive rate is the percentage of people who are told they have cancer but actually don’t. This requires that patients get more testing, which can be costly, sometimes risky and often worrisome.

In comparison, many currently recommended screening tests, such as the Cologuard stool test for colorectal cancer, have false positive rates in the 10% range.

This very low false positive rate also translates into another strength – a very high positive predictive value, or PPV, which is the probability that a positive test result actually means cancer is present. The PPV of the Galleri test was 52% across three annual screens, meaning over half the positive results actually led to a cancer diagnosis. This is good because it gives people confidence that the test is more than 50% correct.

For context, the PPVs of most recommended screening tests – such as stool tests for colorectal cancer, mammography for breast cancer, or the HPV test for cervical cancer – are typically below 10%, meaning most positive results don’t lead to a cancer diagnosis.

The Galleri test also can predict with high accuracy where a cancer originated in the body. In one study of 32,000 U.S. adults age 50 and older who received a Galleri blood test, cancer was diagnosed in about 0.5% of them – 173 patients. Of these patients, the test correctly predicted the cancer type in 91%. This specificity could help clinicians select more targeted evaluations rather than looking for cancer anywhere in the body.

What are the limitations of the Galleri test?

Despite these impressive results, the Galleri test has several major shortcomings.

For one, the test is not as good at detecting cancer in its earliest stages as currently recommended screening tests, which is the main point of a cancer screening test. The test’s ability to detect cancer at all stages was less than 31% over three annual rounds of screening, meaning the test missed 69% of cases. Of the cancers detected in the study, comparing outcomes from getting the Galleri test three years in a row to routine cancer screening, 60% of the cancers detected in the people who got the Galleri test were early stage, which was almost identical to those who didn’t get it.

In addition, the Galleri test did not perform any better than standard screening tests at detecting cancer early. The detection rate for early-stage cancers was only 21% over three years of screening, meaning almost 80% were missed. Cancer is most curable in its early stages, so this shortcoming is a major one. Such a low detection rate can lead to false reassurance from an incorrectly negative test result.

Perhaps the most important shortcoming of the Galleri test is that it hasn’t yet proved that it can save lives or even reduce the risk of being diagnosed with late-stage cancer. The main goal of the trial was to show that the test could reduce the incidence of late-stage cancers over three years of screening – and it failed to do so. In other words, one of the hopes was that the test could reduce the risk of being diagnosed with advanced cancer by finding and treating cancer early – but as of now, there is no evidence to support this.

There was a hint that the incidence of Stage 4 cancer was trending lower by the third year of screening. But more time is needed to determine whether this is a true finding and, if so, whether it leads to a lower risk of dying from cancer.

Requests for comment from GRAIL were not returned.

What did the FDA’s panel recommend?

The FDA advisory panel took three votes. While one of of these votes followed the evidence, two of them were surprisingly counterintuitive.

First, the panel voted 10-0 to recommend that the Galleri test is safe. While undergoing a blood test doesn’t typically involve any substantive risk, a positive result may prompt further testing, such as biopsies, that are riskier than a blood test and can incur additional costs.

These harms can be particularly hard to swallow if the test turns out to be a false alarm, as it will in about half of cases. One study evaluating Galleri’s safety found that 0.6% of those who had the test ended up undergoing an invasive diagnostic procedure, but none experienced serious complications. Hence, the safety vote appears to have been warranted.

Second, the panel voted 6-4 to recommend that the test is effective, though a number of the panelists cast their yes vote on the condition that the company remove the term “early” from the label “multi-cancer early detection” test.

This outcome, however, does not have the evidence to back it up. Available studies indicate the Galleri test does not reduce the incidence of late-stage cancer and performs poorly in detecting early-stage cancer. Additionally, there is no evidence that it lowers the risk of dying from cancer.

Finally, the panel voted 7-2 with one abstention to recommend that the benefits of the Galleri test outweigh the risk. But if there is no proven benefit to the test, how can the benefits outweigh the risks, even if the risk is low?

While the advisory panel acknowledged the test’s serious limitations, it still went ahead and recommended approval. One of the panel members stated that the ability to find more early-stage cancers in a broader population is a benefit, even though that hasn’t been proved yet. “So perhaps my ‘yes’ is a hopeful (vote) rather than an accurate one,” said the panel member.

The problem is that “hope” does not reduce death and disability from cancer.

Should you get the Galleri test or not?

If the FDA agrees with its advisory panel’s recommendation and approves the Galleri test, it will likely be more widely marketed to the American public. Regardless, there remain many caveats, and I believe patients will want to be cautious.

First, FDA approval does not guarantee insurance coverage. The Centers for Medicare and Medicaid Services has a separate coverage determination process, and it is not required to grant coverage to FDA-approved tests. The out-of-pocket cost of the Galleri test is currently US$949.

It remains unclear whether the test can reduce your risk of dying from cancer or being diagnosed with advanced cancer. However, if you’re willing to pay the annual cost of the test, are willing to undergo further testing despite a high rate of false alarms, and are not overly reassured by a falsely negative test result, you can ask your doctor for more information about the test.

What doctors and researchers are certain about is the importance of staying up to date with currently recommended cancer screening tests for colon, breast, cervical and lung cancers, even if you decide to get the Galleri test. These tests are proven to detect early-stage cancer and lower your risk of dying from cancer. That’s the bottom line.

Andrew Wolf serves as Chair of the American Cancer Society's Guideline Development Group. This is a volunteer position. Opinions expressed in this article are those of the author and do not necessarily reflect those of the American Cancer Society.